Heat pump systems have come into high vogue in recent times due to the high cost of fuel and because the systems are of a reversible nature, permitting changeover from winter to summer use, with the system heating the space to be conditioned in the winter and cooling the same in the summer. Heat pump systems employ positive displacement refrigerant compressors normally in the form of single or multiple reciprocating pistons, multiple intermeshed helical screws, rotary sliding vanes, etc. to pressurize a refrigerant, such as Freon, which circulates through a closed refrigerant loop, including one coil within the space to be conditioned and a second coil external of that space. The coil within the space acts as a system evaporator during cooling of the space to be conditioned, with that coil functioning as a system condenser when the space is being heated. This is achieved by alternate reversal of refrigerant flow, and where heat is being discharged into that space, the heat is picked up by the coil external of the space functioning as the system evaporator. Additionally, waste heat may be removed from the space either by that coil or additional coil or coils functioning as system evaporators and the energy may be wasted to the atmosphere. Alternatively, it may be stored for subsequent resupply to the space to be conditioned by means of a heat storage media thermally insulated from the space to be conditioned, and under some circumstances being located within that space. Thermal energy may be picked up by solar radiation in addition to thermal energy picked up by the coil external of the space and normally within the outside air, although, in some cases the outside coil is positioned in the ground for either waste heat discharge to the ground or pickup of heat from the ground.
Solar energy has been fed to heat pump systems. Solar collectors, particularly in residential systems, have been simply placed on the sloping roof of the building facing the predominant source of solar radiation and pickup is achieved by the circulation of a liquid or other medium between the collectors and a storage tank which also includes an evaporator coil forming a part of the closed loop refrigeration system including the compressor and the other coils mentioned above. Such solar collectors introduce a second heat transmission fluid or medium and normally pumps are required to circulate that medium, and where liquids are used, special precautions must be taken, particularly in the winter, to prevent the liquid from freezing and damaging or destroying the solar loop including the collectors themselves.
In the heat pump art itself, systems have been devised, particularly for residential use, which are mounted within the attic and which include duct work connecting the coils situated within the attic and the room or rooms to be conditioned below the attic floor and to the building exterior. An inside or indoor coil mounted within such duct work provides the necessary heat transfer between the refrigerant fluid circulating within the coil and the air flow through the duct work to circulate conditioned air to the room or rooms beneath the attic floor. Further, there have been some attempts to employ solar windows within the roof to permit the interior of the attic to be employed as a solar collector in which the attic air constitutes the media being heated, and which air is either circulated directly to the space to be conditioned or in heat transfer with coils of the heat pump system to achieve indirect thermal energy transfer between the air occupying the attic and that circulated to and from the space being conditioned.
Residential heat pump systems today must be designed so that the system is fully capable of meeting the necessary cooling or heating loads to the space or spaces to be conditioned throughout the year regardless of temperature variation and in a manner that insures maximum efficiency in achieving that conditioning, not only because of the relatively high cost of energy today but because of the need for conservation of our available energy resources. Such systems include an outside air coil, solar source coil, storage coil, inside air coil, hot water coil and the like all operating at different temperatures and within different environments. Since these operating parameters vary from day to day and even from hour to hour depending upon the need for heating, cooling, dissipation, or storage of thermal energy, compressors are required having variable capacity capability and operating efficiently regardless of compressor load variation and also having the capability of permitting both intermediate pressure level return of refrigerant vapor to the compressor or removal from the compressor of refrigerant vapor partially compressed--that is, at intermediates pressure level with respect to compressor suction and full discharge. In the past, such systems have employed complicated conduits, reversing valves and the like to selectively operate the coils in either condensor or evaporator function and hopefully match the coil operating parameters to available vapor return and vapor supply pressures of the compressor.
It is therefore a primary object of the present invention to provide an improved residential heat pump system which may be appropriately attic mounted in terms of much of its componentry, with the roof bearing a solar window and the attic employed as a passive solar collector, and wherein the system incorporates a plurality of elements defining multiple thermal sources and heat sinks to maximize heat pump system efficiency, whether under heating or cooling mode.
It is a further object of this invention to provide an improved attic mounted solar assist multi-source/sink residential heat pump system which employs a plurality of coils functioning in heat source or heat sink fashion and which operate at varying pressure levels, and wherein the heat pump system incorporates a compression module permitting vapor return and vapor discharge at intermediate pressure levels relative to compressor suction and discharge to match coil needs to compressor capability.
It is a further object of the present invention to provide an improved attic mounted solar assist multi-source/sink residential heat pump system in modular form which utilizes both a compression module for acceptance and deliverance of refrigerant vapor at different pressure levels and which is characterized by the absence of a reversing valve and its attendant control, and wherein a plurality of coils function as multiple heat sources or heat sinks and for desired space and component heating and cooling and being connected within a closed refrigeration loop through discharge, suction, liquid feed and liquid drain manifolds common to these elements, and wherein the multiple coils may be connected selectively to either the high side or low side of the compressor and at different pressure levels.